The invention applies to any off-shore platform or similar structure which is designed to be placed on a stationary support structure already in place. There is thus a problem of swell at the time when the platform is installed on said support structure, whether the platform itself floats, or is transported by a barge, or is suspended from the hook of a floating crane, etc.
The platform has piles which, at the end of the operation, must rest on determined locations of the support structure and which must be welded thereto.
The swell makes this platform installing operation particularly difficult because of the danger of the platform striking against its support structure and causing serious damage. Further, welding is also a tricky operation because of the load weight which may be very great.
Preferred embodiments of the present invention make it possible to install such a platform without damaging it by impacts due to the swell, and then to weld the platform to its support structure under very good conditions.